You can't. By setting permissions carefully you'll be able to remove most menu entries for those users, but any menu item that doesn't explicitly check for permissions will appear no matter what. I don't think you can remove the "new" menu or the "dashboard"
link. A better and simpler option for you may be to deny dashboard access completely to the editor role (I'm assuming you meant role and not user up there, as permissions only apply to roles, never to users) and to expose your features through your own custom
route and controllers. Another option may be to use the new features in Orchard 1.5 (custom forms, content permissions, etc.).